1. Field of the Invention
This invention relates to packages, and more particularly, to a package with replaceable resilient cushions for holding disk products such as substrate wafers, semi-conductor wafers or computer memory disks between which the wafers are suspended to prevent sliding or pivoting of the wafers on the edge profile, thus eliminating particle generation and damage to the wafers.
2. Description of the Prior Art
A variety of packages for holding and transferring substrate wafers are known in the prior art. For example, U.S. Pat. No. 5,046,615 to Nentl discloses a disk shipper device utilizing downwardly extending dentate leaves or resilient flanges in a row of crenate scallops in the cover to maintain the wafers or disks in an upright parallel spaced part alignment and provide secure positioning of the disks to prevent transverse or lateral motion within the last shipper.
U.S. Pat. No. 4,966,284 to Gregorson et al., discloses a substrate package container for storing and transporting substrate wafers. The container disclosed in this patent includes opposing rows of articulated cantilevered horizontal arms with centered V-grooves on each end for engaging the wafer.
U.S. Pat. No. 4,793,488 to Mortensen discloses a two part package for storing and transporting semiconductor wafers. This package contains a plurality of wafer contactors which exert a spring pressure against the wafers to secure the wafers in place.
U.S. Pat. No. 4,653,636 to Armstrong discloses a high temperature wafer boat. This wafer boat contains conventional ribs and a bottom supporting rib, side supporting rails and side retaining rails. These rails have aligned grooves to maintain the positioning of the wafers.
U.S. Pat. No. 4,588,086 to Koez discloses a two-part substrate carrier having a transparent lid. The base portion contains semi-circular V-shaped grooves. The cover also includes V-shaped grooves for engaging the top of the wafer.
The Voss et al. 4,555,024 patent discloses a packaging unit for semiconductor wafers which contains spring tongues in the base to support surfaces and inwardly projecting retention cones in the lid. The wafers are fixed at only four contact points. The goal of this design is to maintain minimal contact with the wafer.
U.S. Pat. No. 4,450,960 to Johnson discloses a package which is contoured and contains flexible fingers which space and secure the wafers and provides an upward pressure towards the package top with respect to the package bottom.
U.S. Pat. No. 4,160,504 to Kudlich describes a package having a plurality of parallel, laterally extending guide ribs formed opposite each other and a plurality of knobs which cooperate to maintain the disks in an upright position.
U.S. Pat. No. 4,043,451 to Johnson discloses still another shipping container for semiconductor wafers. The lid has interior wafer locating ribs and resilient, curved wafer supports beneath and over the edges of the wafer. The base contains an elongated panel of soft springy plastic with a corrugated wafer engaging face.
While significant improvements in disk package technology are set forth in the prior art references discussed above, real problems continue to exist even with the use of these prior art packages. Many of these problems arise given the nature of the disks which they are designed to contain. Such disks are easily breakable, easily scratched, and are therefore very fragile. Particles or other environmental contamination easily damage the substrate wafers. Certain other prior art packages described above can protect the disks from the external environment. However, when such packages are used, the disks have become damaged due to the packaging itself and from the internal environment of the package. The package interior becomes contaminated by particles which are generated as the disks pivot, slide or rotate on their edge profiles against the packaging. Internal contamination becomes more prevalent as the thermoplastics used to cushion or retain the disks in the package lose their elastic memory so that the disks are no longer securely held. This lose of elastic memory is known as flexural creep. When flexural creep occurs, the packaged disks can rotate or slide on their edge profiles generating particles which can damage or contaminate the wafer Substrates. Thus, these packages damage the highly sensitive face surfaces used in the manufacturing of integrated circuits in addition to the edges of the substrate wafers.
The present invention overcomes the disadvantages of the prior art by providing a novel cushion device in a ridged transparent, thermoplastic package having a base and a cover. The cushion is made from an elastomeric or flexible thermoplastic material having resilient characteristics which eliminate the rapid loss of elastic memory present in other disk cushion materials. A complementing elastomeric or flexible or rigid thermoplastic cushion may be located in the base so that when the package is used, the disks are sandwiched between the elastomeric cushions and firmly held in place by them. The configuration of the cushion incorporating independent disk engaging members, in addition to the material, aids in preventing damage to the disks.
The first cushion embodiment consists of a plurality of independent disk engaging members. Each disk engaging member has a flexible disk engaging edge and two legs extending perpendicular from the disk engaging edge on opposing ends. The plurality of disk engaging members are joined at the leg portions opposite the disk engaging edge. Each disk engaging member is resilient and independently deformable to securely engage the edge of a disk.
In a second cushion embodiment, the cushion has a plurality of disk engaging edges formed in a concave surface. Two legs extend perpendicular on either side of the wafer engaging edges formed in the concave surface.
The disk engaging edges on both these cushion embodiments have angled surfaces extending outwardly on either side. This allows the edge of the disk to be firmly centered and secured between the outwardly extending surfaces.
When the package is closed, the disks are firmly held between the cushions located in the package base and the package cover in such a way that the possibility of damage to the disk is greatly reduced as compared to the prior art packages discussed above.